Chemical double-layer capacitor power source for electromechanical thrust vector control actuator

Abstract

Power sources for electrical actuation systems need to be made as compact as possible for many potential applications. Size and weight constraints require that the energy and power densities of the source be as large as possible. While, in general, it is not possible to optimize both these parameters simultaneously, chemical double-layer (CDL) capacitor technology offers an excellent combination of the desirable energy and power density characteristics required in a source for these applications. The work presented here focuses on the design, testing, and evaluation of the CDL capacitor technology in combination with batteries as a unique power source for electrical actuation systems. In this research effort CDL capacitor technology was applied in the design and development of a power source for thrust vector control electromechanical actuators currently being developed for use on the Space Shuttle's solid rocket boosters. CDL capacitors have many properties that make them well suited for actuator applications. Among them are that they have the highest demonstrated energy density for capacitive storage (about a factor of 5-10 less than NiCd batteries), have power densities up to 50 times greater than NiCd batteries, are capable of 500,000 charge-discharge cycles, can be charged at extremely high rates, and have nonexplosive failure modes. Thus, CDL capacitors exhibit a combination of desirable battery and capacitor characteristics.